1. Field of the Invention
The present invention relates to an information recording medium and a method for recording and reproducing the same, and particularly to an information recording medium on which tracking servo information is magnetically preformat-recorded, and a method for recording and reproducing for an information recording medium in which at least one of recording and reproduction of information is carried out while reading servo information using the information recording medium and performing tracking. The present invention also relates to an information recording method in which information is recorded on the image recording medium by a magneto-optic system utilizing near field light. Further, the present invention relates to a manufacturing method of an information recording medium, and particularly to a manufacturing method of an information recording medium on which tracking servo information is magnetically preformat-recorded.
2. Description of the Related Art
With a rapid increase in the amount of information to be handled by a personal computer, large-capacity and low-cost information recording media which permit reduction of access time have been developed one after another. Examples of such large capacity information recording media include a built-in magnetic recording medium such as a hard disk, and a removable magnetic recording medium such as a Zip disk developed by Iomega Corp.(in U.S.). The hard disk or Zip disk realizes large capacity recording by reducing the width of each track to increase a track density. In order that a narrow track be accurately scanned by a magnetic head and a recording signal be reproduced at a favorable signal to noise ratio (S/N), tracking servo technique in which the position of a magnetic head is corrected by detecting relative displacement of the magnetic head and the track, performs an important function.
In the hard disk or Zip disk, a tracking servo signal, an address information signal, a reproduction clock signal and the like are in advance recorded (preformat-recorded) with high positional accuracy at the time of manufacturing magnetic recording media. A region in which these signals are recorded, that is, a servo region is disposed discretely to the surface of a disk, and a magnetic head accurately scans a track while confirming and correcting the position of the head by reproducing these signals.
As a next-generation high density recording system, a recording system utilizing near field light (a near-field light recording system) is considered to be effective. In this recording system, it is expected that high density recording of 100 gigabits/inch2 or more becomes possible.
Near field light is non-propagation light which is generated when light scatters and diffracts in a micro-aperture having a diameter which is the wavelength or less, and is localized in the vicinity of the micro-aperture (that is, in a region from a light emission end of the micro-aperture to the wavelength of the light). Further, near field light can also be generated by condensing light in a solid immersion lens (SIL). Due to light recording using the near field light, a recording mark smaller than a recording mark obtained by normal light recording can be formed, thereby resulting in a remarked increase in the surface recording density of information.
The near field light exists only in a region from a light emission end of the micro-aperture or SIL, which is a recording head, to the wavelength of light. Therefore, recording and reproducing needs to be carried out in such a manner that means for generating near field light and a detector (head) of the light are disposed extremely in the vicinity of the recording medium (specifically, in a region apart from the recording medium by a distance of several tens nm or less).
However, accompanied with a further increase in the recording density, the track width is becoming narrower. In a conventional servo system, there exists a problem in that accurate scanning of tracks by a magnetic head (servo following) is not permitted. There is a high possibility that a problem may arise in servo following, particularly in the recording density of 100 gigabits/inch2 or more. Further, if a trial to reliably perform servo following is made by increasing the ratio of a servo region to the area of a disk, a recording region is reduced and a large recording capacity is difficult to maintain.
Further, in an optical disk, a servo system is employed wherein tracking is performed by using a tracking guide having a land/groove structure in which tracks are provided concentrically or spirally in the disk. However, this system has a problem in that large unevenness exists on the disk surface. Accordingly, in the next-generation high density recording system in which a detector needs to be disposed extremely in the vicinity of a recording medium, it is difficult to realize a stable running or flying state of the head.
Moreover, exact positioning accuracy is required by preformat-recording. Therefore, conventionally, a magnetic recording medium is built in a drive, and thereafter, recording is carried out by a magnetic head which is exactly position-controlled by using a servo recording device dedicated thereto.
However, the amount of signals to be preformat-recorded increases accompanied with the increase in magnetic recording density. Therefore, there exists a problem in that a lot of time is required for preformat-recording, which leads to deterioration of production efficiency.
Further, there has also been proposed a method in which a magnetic-transfer master carrier with a predetermined magnetization pattern being formed thereon by a magnetic layer, is used and the predetermined magnetization pattern is transferred to a slave medium to allow preformat-recording. However, in the conventional transfer method, it was necessary to use a magnetic-transfer master carrier having coercive force (HC) which is at least three times the coercive force of the slave medium such that the magnetization pattern of the magnetic-transfer master carrier should not be demagnetized even if it is excited by an external magnetic field. When a flat magnetic body is partially magnetized, the antimagnetic force of a magnetic body used in a magnetic recording medium for high density recording is a high value, that is, 2000 Oe or thereabouts, and the coercive force of the magnetic-transfer master carrier is 6000 Oe or more. Accordingly, a certain magnetic material can only be used for the magnetic-transfer master carrier, and it was virtually difficult to form a minute magnetic pattern.
The present invention has been achieved in view of the problems of the above-described prior art, and an object thereof is to provide an information recording medium which permits accurate tracking servo, particularly, an information recording medium which allows stable running of the head even when a detector is disposed extremely in the vicinity of the recording medium. Another object of the present invention is to provide a method for recording and reproducing for an information recording medium, in which recording (high density recording) and reproducing of signals can be carried out at a favorable S/N by carrying out at least one of recording and reproducing of information while accurately performing tracking servo.
Further, still another object of the present invention is to provide a manufacturing method of an information recording medium, in which an information recording medium which permits accurate tracking servo can be manufactured precisely in a short time.
In order to achieve the above-described objects of the present invention, there are provided a 1st to a 39th aspects.
A 1st aspect of the present invention is an information recording medium comprising a substrate disposed thereon a magnetic recording layer for magnetically recording information,
wherein the magnetic recording layer is in advance magnetized concentrically or spirally around a center of a disk for tracking and is disposed in such a manner that magnetized regions magnetized in different directions are alternately arranged in a radial direction of the disk.
A 2nd aspect of the present invention is an information recording medium according to the 1st aspect, wherein the directions in which the magnetized regions are magnetized for tracking are perpendicular to a surface of the disk.
A 3rd aspect of the present invention is an information recording medium according to the 1st aspect, wherein the substrate is disk-shaped, flexible and nonmagnetic.
A 4th aspect of the present invention is an information recording medium according to the 1st aspect, wherein discrete servo fields are in advance magnetically recorded in the magnetic recording layer.
A 5th aspect of the present invention is an information recording medium according to the 1st aspect, wherein the magnetized regions are each formed so as to meander at a fixed frequency.
A 6th aspect of the present invention is an information recording medium according to the 1st aspect, wherein a magnetized region magnetized in a predetermined direction is wider than a magnetized region magnetized in a direction which is different from the predetermined direction.
A 7th aspect of the present invention is a method for recording and reproducing for an information recording medium, in which the information recording medium comprising a substrate disposed thereon a magnetic recording layer for magnetically recording information, the magnetic recording layer being in advance magnetized concentrically or spirally around a center of a disk for tracking and being disposed in such a manner that magnetized regions magnetized in different directions are alternately arranged in a radial direction of the disk, is used, comprising:
at least one of recording and reproducing information, while performing tracking based on a difference in the directions in which the magnetized regions of the magnetic recording layer are magnetized.
A 8th aspect of the present invention is a method for recording and reproducing for an information recording medium according to the 7th aspect, wherein the magnetized regions are irradiated with linearly polarized light, a direction in which the plane of polarization of reflected light rotates corresponding to the difference in the directions in which the magnetized regions are magnetized is detected, and the tracking is preformed based on the detected direction in which the plane of polarization of the reflected light rotates.
A 9th aspect of the present invention is a method for recording and reproducing for an information recording medium according to the 8th aspect, wherein the linearly polarized light is near field light.
A 10th aspect of the present invention is a method for recording and reproducing for an information recording medium according to the 7th aspect, wherein the tracking is performed by using a three-beam method in which directions in which the planes of polarization of reflected lights of two tracking beams rotate are detected respectively and the two detected values are compared.
A 11th aspect of the present invention is a method for recording and reproducing for an information recording medium, in which the information recording medium comprising a substrate disposed thereon a magnetic recording layer for magnetically recording information, the magnetic recording layer being in advance magnetized concentrically or spirally around a center of a disk for tracking and being disposed in such a manner that magnetized regions magnetized in different directions are alternately arranged in a radial direction of the disk, and discrete servo fields being in advance magnetically recorded in the magnetic recording layer, is used, comprising:
at least one of recording and reproducing information, while performing tracking based on a difference in the directions in which the magnetized regions of the magnetic recording layer are magnetized; and
performing sector servo based on the discretely recorded servo fields.
A 12th aspect of the present invention is a method for recording and reproducing for an information recording medium, in which the information recording medium comprising a substrate disposed thereon a magnetic recording layer for magnetically recording information, the magnetic recording layer being in advance magnetized concentrically or spirally around a center of a disk for tracking and being disposed in such a manner that magnetized regions magnetized in different directions are alternately arranged in a radial direction of the disk, and the magnetized regions being each formed so as to meander at a fixed frequency, is used, comprising:
at least one of recording and reproducing information, while performing tracking based on a difference in the directions in which the magnetized regions of the magnetic recording layer are magnetized; and
generating at least one of a clock signal and an address signal based on the frequency at which the magnetized regions meander.
A 13th aspect of the present invention is a method for recording and reproducing for an information recording medium according to the 7th aspect, wherein information is recorded in the magnetized regions.
A 14th aspect of the present invention is a method for recording and reproducing for an information recording medium according to the 7th aspect, wherein information is recorded in the magnetized regions by using one of a light modulation system or a magnetic modulation system.
A 15th aspect of the present invention is a method for recording and reproducing for an information recording medium according to the 7th aspect, wherein information is magnetically recorded in such a manner in which the magnetized regions of the magnetic recording layer are irradiated with near field light and a portion irradiated with the near field light is heated to a substantial Curie temperature, and a magnetic field having a predetermined direction thereof is applied to the portion from a magnetic head.
A 16th aspect of the present invention is a method for recording and reproducing for an information recording medium according to the 7th aspect, wherein information is magnetically recorded only in magnetized region magnetized in a predetermined direction.
A 17th aspect of the present invention is a method for recording and reproducing for an information recording medium according to the 16th aspect, wherein the magnetized region magnetized in the predetermined direction is wider than a magnetized region magnetized in a direction which is different from the predetermined direction.
A 18th aspect of the present invention is a method for recording and reproducing for an information recording medium according to the 16th aspect, wherein the magnetized region magnetized in the predetermined direction is divided into a plurality of tracks and information is recorded thereon.
A 19th aspect of the present invention is a method for recording and reproducing for an information recording medium according to the 10th aspect, wherein the magnetized regions are irradiated with linearly polarized light, a direction in which the plane of polarization of reflected light rotates corresponding to the difference in the directions in which the magnetized regions are magnetized is detected, and information recorded in the magnetized regions is read based on the detected direction in which the plane of polarization of the reflected light rotates.
A 20th aspect of the present invention is a method for recording and reproducing for an information recording medium according to the 7th aspect, wherein electric current is made generate due to magnetism of the magnetized regions by electromagnetic induction, a direction in which the electric current flows corresponding to the difference in the directions in which the magnetized regions are magnetized is detected, and information recorded in the magnetized regions is reproduced based on the detected direction in which the electric current flows.
A 21st aspect of the present invention is a method for recording and reproducing for an information recording medium according to the 7th aspect, wherein electrical resistance is made to change due to magnetism of the magnetized regions, and a changed amount of the electrical resistance is detected, and information recorded in the magnetized region is reproduced based on the detected changed amount of the electrical resistance,.
A 22nd aspect of the present invention is a method for recording and reproducing for an information recording medium according to the 7th aspect, wherein at least one of recording and reproducing of information is carried out in such a manner that the surface of the magnetic recording layer and the magnetic head are made close to each other with a distance therebetween of no greater than 100 nm on a disk-surface average.
A 23rd aspect of the present invention is an information recording medium according to the 1st aspect, wherein the substrate is disk-shaped and smooth.
A 24th aspect of the present invention is an information recording medium according to the 23rd aspect, wherein a direction of magnetization for tracking and a direction of magnetization for recording and reproducing information are each made perpendicular to the surface of the disk.
A 25th aspect of the present invention is an information recording medium according to the 23rd aspect, wherein a protective layer is formed on the magnetic recording layer.
A 26th aspect of the present invention is an information recording medium according to the 25th aspect, wherein a lubricating film is formed on the protective layer.
A 27th aspect of the present invention is an information recording medium according to the 26th aspect, wherein a total thickness of the protective layer and the lubricating film is no greater than 100 nm.
A 28th aspect of the present invention is an information recording medium according to the 23rd aspect, wherein a reflective film is formed between the substrate and the magnetic recording layer.
A 29th aspect of the present invention is an information recording medium according to the 23rd aspect, wherein the substrate is a flexible and non-magnetic base plate.
A 30th aspect of the present invention is a method for recording and reproducing for an information recording medium according to the 7th aspect, wherein information is magnetically recorded in such a manner in which the magnetized regions of the magnetic recording layer are irradiated with near field light and a portion irradiated with the near field light is heated to a substantially Curie temperature, and a magnetic field having a predetermined direction thereof is applied to the portion from a magnetic head.
A 31st aspect of the present invention is a method for recording and reproducing for an information recording medium according to the 7th aspect, wherein the predetermined direction of the magnetic field is perpendicular to the surface of the disk.
A 32nd aspect of the present invention is a method for recording and reproducing for an information recording medium according to the 30th aspect, wherein information is recorded in the magnetic recording layer by applying the magnetic field having the predetermined direction thereof, from a side of the magnetic recording layer opposite to the base plate.
A 33rd aspect of the present invention is a method for recording and reproducing for an information recording medium according to the 30th aspect, wherein, with the magnetic field having the predetermined direction thereof being applied from the magnetic head to the magnetized regions of the magnetic recording layer, the near field light modulated in accordance with a recording signal is applied to the magnetized regions to thereby allow magnetic recording of information.
A 34th aspect of the present invention is a method for recording and reproducing for an information recording medium according to the 30th aspect, wherein, with near field light being applied to the magnetized regions of the magnetic recording layer, the magnetic field having the predetermined direction thereof, which is modulated in accordance with a recording signal, is applied to the magnetized regions from the magnetic head to thereby allow magnetic recording of information.
A 35th aspect of the present invention is a method for recording and reproducing for an information recording medium according to the 30th aspect, wherein the base plate is flexible and non-magnetic.
A 36th aspect of the present invention is a method for recording and reproducing for an information recording medium according to the 30th aspect, wherein information is recorded in such a manner that the surface of the magnetic recording layer and the magnetic head are moved close to each other with a distance therebetween of no greater than 100 nm.
A 37th aspect of the present invention is a method for recording and reproducing for an information recording medium according to the 30th aspect, wherein the tracking is performed in such a manner that a reflective film is formed between the base plate and the magnetic recording layer, and light reflected by the surface of the magnetic recording layer when near field light is applied to the information recording medium and light transmitted through the magnetic recording layer and reflected by the reflective film are detected.
A 38th aspect of the present invention is a method for recording and reproducing for an information recording medium according to the 30th aspect, wherein information is recorded by dividing a magnetized region magnetized in the predetermined direction into a plurality of tracks.
A 39th aspect of the present invention is a method of manufacturing an information recording medium, the information recording medium comprising a magnetic recording layer for magnetically recording information, the magnetic recording layer being in advance magnetized concentrically or spirally around the center of a disk for tracking such that magnetized regions magnetized in different directions are alternately arranged in a radial direction of the disk, the method comprising the steps of:
magnetizing the entire magnetic recording layer in a predetermined direction;
adhering a magnetic layer of a disk-shaped master carrier to a surface of the magnetic recording layer of the information recording medium, the master carrier being formed concentrically or spirally around a center of the disk and having an unevenness pattern in which at least convex portions are covered by the magnetic layer; and
applying a magnetic field having a direction thereof which is different from the predetermined direction, to the magnetic recording layer via the magnetic layer to thereby reverse a magnetized direction of a portion of the magnetic recording layer to which the magnetic layer adheres.
According to the first aspect of the present invention, the information recording medium has, on the substrate (support), the magnetic recording layer for magnetically recording information. The magnetic recording layer is in advance magnetized for tracking such that magnetized regions magnetized in different directions are alternately arranged in the radial direction of the disk. Therefore, tracking can be performed based on the difference in the directions in which magnetized regions are magnetized. Further, the magnetic recording layer is in advance magnetized concentrically or spirally around the center of the disk for tracking, and tracking can be continuously performed and accurate tracking servo can be performed. Moreover, tracking can be performed based on the difference in the directions in which the magnetized regions are magnetized, and it is not necessary to form unevenness on the surface of the medium. Even when a detector is disposed extremely in the vicinity of the recording medium, a stable running or flying state of the head can be realized.
In the above-described information recording medium, the direction in which the magnetic recording layer is magnetized for tracking is preferably made perpendicular to the surface of the disk. When the direction of magnetization is made perpendicular to the surface of the disk, there is no possibility that the magnetized regions magnetized in different directions and alternately arranged in the radial direction of the disk may weaken magnetic force one another. As a result, the magnetic force of each magnetized region becomes stable.
In order to form the substrate of the information recording medium, aluminum, glass, polycarbonate and the like may be used in the same way as in general hard disk drives. Preferably, a disk-shaped flexible and non-magnetic substrate is used. When the flexible and non-magnetic substrate is used as the substrate, head crash caused when the disk contacts the head is alleviated. Even when the head is disposed extremely in the vicinity of the recording medium as in the next-generation high density recording system using a flying head, the head and the disk stably slide in contact with each other, and stable running of the head becomes possible. Further, since the flexible and non-magnetic substrate is used as the base material, the information recording medium can be manufactured at a low cost.
A reflective film is preferably formed between the substrate and the magnetic recording layer. Even when near field light is used as recording and reproducing light, near field light which is non-propagation light, is converted to propagation light and is reflected by the reflective film. Therefore, when light into which the near field light is reflected by the surface of the magnetic recording layer, is detected utilizing a magnetic Kerr effect, the reflected light based on the propagation light is detected by Faraday effect and S/N of a detection signal improves. That is, so-called enhancement effect can be obtained.
The discrete servo fields can be in advance magnetically recorded in the magnetic recording layer. Due to the discrete servo fields being in advance magnetically recorded in the magnetic recording layer, the servo fields are read out by utilizing a magneto-optical effect such as Kerr effect at the time of recording or reproducing and sector servo can be performed. Due to the tracking servo and the sector servo being used together, accurate tracking becomes possible and the access speed to a predetermined area becomes higher.
The magnetized regions can be formed so as to extend in a meandering (serpentine) line at a fixed frequency. When so-called wobbles are applied to the magnetized regions, it is possible to detect a tracking signal and also generate a clock signal or an address signal.
In accordance with the seventh aspect of the present invention, the method for recording and reproducing an for information recording medium has a feature that the information recording medium of the present invention is used and at least one of recording and reproducing of information is carried out while carrying out tracking based on the difference in the directions in which the magnetized regions of the magnetic recording layer are magnetized. In the information recording medium of the present invention, the magnetic recording layer is in advance magnetized concentrically or spirally around the center of the disk for tracking and is provided such that the magnetized regions magnetized in different directions are alternately arranged in the radial direction of the disk. Accordingly, when at least one of recording and reproducing of information is carried out using the information recording medium, at least one of the recording and the reproducing can be carried out while accurately performing tracking servo based on the difference in the directions in which the magnetized regions are magnetized, and recording and reproducing of a signal can be carried out at a favorable S/N.
In the above-described method, the magnetized regions are irradiated with linearly polarized light and the direction in which the plane of polarization of reflected light rotates corresponding to the difference in the directions in which the magnetized regions are magnetized, is detected, and based on the detected direction in which the plane of polarization of the reflected light rotates, tracking can be performed. When at least one of recording and reproducing of information is carried out, the magnetized regions are irradiated with linearly polarized light and the direction in which the plane of polarization of the reflected light rotates corresponding to the difference in the directions in which the magnetized regions are magnetized, can be detected by utilizing a magnetic Kerr effect. Based on the detected direction in which the plane of polarization of the reflected light rotates, tracking can be performed.
As the linearly polarized light used for tracking, near field light can be used. Further, a tracking error detection system for tracking is preferably a three-beam method in which the directions in which the planes of polarization of light into which two tracking beams are reflected, are detected and the two detection values are compared with each other.
In the above-described method, information is preferably recorded in the magnetized regions. Since information is recorded in the magnetized regions magnetized in advance for tracking, it is possible to prevent reduction in the recording capacity caused by an increase in the area of a servo region.
An information recording method has a feature that information is recorded in the magnetized regions by a light modulation system or a magnetic modulation system. The magnetic recording layer of the information recording medium is irradiated with light and a portion irradiated with the light is heated to a Curie temperature or thereabouts, and due to a magnetic field being applied to the magnetic recording layer from the magnetic head, information is magnetically recorded. The system for recording information may either the light modulation system or the magnetic modulation system. Further, light used for the recording may be light into which laser light oscillated by semiconductor laser or the like is condensed by an optical lens in a general manner. Further, the recording can be carried out while effecting irradiation of near field light. As the laser light source, a semiconductor laser having an oscillation wavelength, for example, ranging from 400 to 780 nm can be used. In order to increase the recording density, blue-violet semiconductor laser, blue-violet SHG laser comprised of infrared semiconductor laser and a wavelength conversion element (SHG), or the like is preferably used. The blue-violet semiconductor laser having a wavelength of 405 nm or thereabouts is particularly preferable.
When information is recorded, information can be magnetically recorded only in a magnetized region magnetized in a predetermined direction. In this case, when the magnetized region magnetized in the predetermined direction is made wider than a magnetized region magnetized in a different direction, format efficiency improves. Further, information can be recorded in such a manner that the magnetized region magnetized in the predetermined direction can be divided into a plurality of tracks. In this case as well, format efficiency improves.
In order to reproduce recorded information, a method is provided, wherein the magnetized regions are irradiated with linearly polarized light, and the direction in which the plane of polarization of the reflected light rotates corresponding to the difference in the directions in which the magnetized regions are magnetized, is detected, and base on the detected direction in which the plane of polarization of the reflected light rotates, information recorded in the magnetized regions is reproduced. According to this method, the information recorded in the magnetized regions can be reproduced by utilizing a magnetic Kerr effect.
Another method for reproducing recorded information is a method in which electric current is generated by electromagnetic induction from magnetism of the magnetized regions, and the direction in which electric current flows corresponding to the difference in the directions in which the magnetized regions are magnetized, is detected, and based on the detected direction of electric current, information recorded in the magnetized regions is reproduced. According to this method, the information recorded in the magnetized regions can be reproduced by utilizing electromagnetic induction.
Still another method for reproducing recorded information is a method in which electrical resistance is changed due to magnetism of the magnetized regions and a variation in electrical resistance is detected, and based on the detected variation in electrical resistance, information recorded in the magnetized regions is reproduced. According to this method, the information recorded in the magnetized regions can be reproduced by utilizing a magnetic resistance effect.
When recording and reproducing of information is carried out, preferably, recording and reproducing may be carried out in such a manner that the surface of the magnetic recording layer and the magnetic head are made close to each other with a distance therebetween of 100 nm or less on a disk-surface average. That is, it is preferable that recording and reproducing of information be carried out in such a state that the information recording medium and the magnetic head stably slide in contact with each other. Such state can be realized when, for example, a disk-shaped flexible and non-magnetic substrate is used. So long as the surface of the magnetic recording layer and the magnetic head are moved close to each other with a distance therebetween of 100 nm or less on a disk-surface average, high density recording utilizing near field light becomes possible.
In accordance with the twenty-third aspect of the present invention, the information recording medium comprises a disk-shaped smooth (flat) base plate having no groove or pit (hole) used for tracking servo or data recording, and, formed on the base plate, a magnetic recording layer for magnetically recording information. Therefore, as the same as the information recording medium according to the first aspect, based on the difference in the magnetized directions in the magnetized regions, tracking can be performed. Further, tracking can be continuously performed and accurate tracking servo can be performed. Moreover, it is not necessary to form unevenness (convexoconcave) on the disk-shaped smooth base plate. Even when the detector is disposed extremely in the vicinity of the recording medium, a stable running or flying state of the head can be realized.
In the information recording medium according to the twenty-fourth aspect of the present invention, the directions in which the magnetized regions are magnetized are made perpendicular to the surface of the disk. Therefore, as described above, the magnetic force of each magnetized region becomes stable.
In the information recording medium according to the twenty-fifth and twenty-sixth aspects of the present invention, it is possible to prevent corrosion of the magnetic recording layer, or abrasion caused by near contact or contact-sliding of the head and the disk at the time of recording and reproducing information, and also improve running durability and corrosion resistance. Further, no groove or pit is used by (formed in) the base plate of the present invention. As a result, recording or reproduction of information can be carried out in such a manner that the surface of the magnetic recording layer and the head are close to each other with a distance between of 100 nm or less in an entire data area, that is, the information recording medium and the head stably slide in contact with each other. Therefore, high density recording using near field light becomes possible.
In the information recording medium according to the twenty-eighth aspect of the present invention, since the reflective film is formed, in magneto optic recording utilizing normal light, the reflectance becomes higher and the strength of a signal increases. Further, even when near field light is used, as described above, when reflected light of which near field light is reflected by the surface of the magnetic recording layer, is detected by utilizing a magnetic Kerr effect, enhancement effect can be obtained.
In the information recording medium according to the twenty-ninth aspect of the present invention, since the flexible and non-magnetic base plate is used as the base plate, as described above, crash caused when the head and the disk come in contact with each other is alleviated. Even when the head is disposed extremely in the vicinity of the recording medium, the head and the disk stably slide in contact with each other, and stable running of the head becomes possible.
In addition to a concentric or spiral tracking signal, as described above, discrete servo fields may also be in advance magnetically recorded in the magnetic recording layer of the information recording medium.
In the above-described information recording medium, the magnetized regions of the magnetic recording layer may be formed so as to extend in a meandering line at a fixed frequency. When so-called wobbles are applied to the magnetized regions, it is possible to detect a tracking signal and also generate a clock signal or an address signal. Further, a tracking error detection system for tracking is preferably a three-beam method described above.
As described above, the information recording medium may also be used such that information may be magnetically recorded only in magnetized regions magnetized in a predetermined direction.
Further, light used for recording and reproducing information of the information recording medium may be light such that laser light oscillated by semiconductor laser or the like is condensed by an optical lens in a general manner. Alternatively, recording can be carried out while effecting irradiation of near field light.
The information recording medium used by the method for recording and reproducing for an information recording medium according to the thirtieth aspect of the present invention has a magnetic recording layer formed on a disk-shaped smooth base plate. Accordingly, as the same as the information recording medium according to the first aspect, based on the difference in the magnetized directions in the magnetized regions, tracking can be performed. Further, tracking can be continuously performed and accurate tracking servo can be performed. Moreover, it is not necessary to form unevenness (convexoconcave) on the disk-shaped smooth base plate. Even when the detector is disposed extremely in the vicinity of the recording medium, a stable running or flying state of the head can be realized.
Information is magnetically recorded, using the information recording medium, in the magnetized region magnetized in advance for tracking. Therefore, it is possible to prevent reduction in the recording capacity caused by an increase in the area of a servo region. Further, a portion of the magnetized region irradiated with near field light is heated to a Curie temperature or thereabouts by being irradiated with the light, and information is magnetically recorded by applying a magnetic field in which magnetic force acts in a predetermined direction from the magnetic head. Therefore, a recording mark smaller than a recording mark formed by normal light recording can be formed and high density recording can be carried out. Further, tracking is continuously performed as described above and accurate tracking servo can be performed. As a result, recording of a signal at a favorable S/N can be carried out.
The discrete servo fields may be in advance magnetically recorded together with a concentric or spiral tracking signal in the magnetic recording layer of the information recording medium used for recording of information, as described above.
Further, the magnetized regions on the magnetic recording layer of the information recording medium can be formed so as to extend in a meandering line at a fixed frequency, as described above.
Moreover, in the above-described information recording medium, the magnetized regions magnetized in a predetermined direction each may be made wider than a magnetized region magnetized in a different direction as described above.
In the method for recording and reproducing for an information recording medium according to the thirty-first aspect of the present invention, information is magnetically recorded by applying a magnetic field perpendicular to the surface of the disk (that is, vertical magnetization). As a result, recording bits magnetized in different directions may be disposed adjacent to each other and may not weaken magnetic force each other. As a result, the magnetic force of a recording region becomes stable.
In the method for recording and reproducing for an information recording medium according to the thirty-second aspect of the present invention, near field light exists only in a region starting from an emission end and less than a wavelength of the light. Therefore, it is necessary that recording be carried out with the emission end and the detector being disposed extremely in the vicinity of the recording medium.
In the method for recording and reproducing for an information recording medium according to the thirty-third aspect of the present invention, recording of information can be carried out by a so-called light modulation recording system.
In the method for recording and reproducing for an information recording medium according to the thirty-fourth aspect of the present invention, recording of information can be carried out by a so-called magnetic modulation recording system.
In the method for recording and reproducing for an information recording medium according to the thirty-fifth aspect of the present invention, the flexible and non-magnetic base plate is used as the base plate.
In the method for recording and reproducing for an information recording medium according to the thirty-sixth aspect of the present invention, it is preferable that recording of information may be carried out in a state in which the information recording medium and the magnetic head stably slide in contact with each other. This state can be realized when a disk-shaped flexible and non-magnetic base plate is used.
In the method for recording and reproducing for an information recording medium according to the thirty-seventh aspect of the present invention, near field light which is non-propagation light is converted to propagation light and reflected by the reflective film. When light into which near field light is reflected by the surface of the magnetic recording layer is detected by utilizing a magnetic Kerr effect, the enhancement effect can be obtained, as described above. Further, when information is reproduced by utilizing a magnetic Kerr effect as well, an enhancement effect can be obtained similarly. Further, as a tracking error detection system for tracking, the three-beam method is used, as described above.
In the method for recording and reproducing for an information recording medium according to the thirty-eighth aspect of the present invention, when information is recorded in the magnetized region magnetized in the predetermined direction, the magnetized region is divided into a plurality of tracks for recording, thereby improvement in format efficiency.
The information recording medium manufactured by the manufacturing method according to the thirty-ninth aspect of the present invention has the magnetic recording layer for magnetically recording information. Since the magnetic recording layer is in advance magnetized for tracking such that the magnetized regions magnetized in different directions are alternately arranged in the radial direction of the disk, tracking can be performed based on the difference in the directions in which the magnetized regions are magnetized. Further, the magnetic recording layer is in advance magnetized concentrically or spirally around the center of the disk for tracking. Therefore, tracking can be continuously performed and accurate tracking servo can also be performed. Moreover, tracking can be performed based on the difference in the directions in which the magnetized regions are magnetized, and therefore, it is not necessary to form unevenness on the surface of the medium. Even when the detector is disposed extremely in the vicinity of the recording medium, a stable running or flying state of the head can be realized.
In the manufacturing method according to the thirty-ninth aspect of the present invention, the information recording medium is manufactured in such a manner that the magnetic recording layer is entirely magnetized in a predetermined direction and formed concentrically or spirally around the center of the disk, and a magnetic layer of a disk-shaped master carrier having an unevenness pattern in which at least convex portions are covered by the magnetic layer, is closely applied to the surface of the magnetic recording layer of the information recording medium, and a magnetic field in which magnetic force acts in a direction different from the predetermined direction is applied to the magnetic recording layer via the magnetic layer, to thereby reverse a direction in which a portion with the magnetic layer applied thereto is magnetized. Due to the magnetic field being applied to the magnetic recording layer via the magnetic layer of the master carrier, a large quantity of information can be recorded in an extremely short time and excellent productivity is obtained. Further, static recording can be carried out without changing the relative positions of the master carrier and the information recording medium, and preformat-recording can be precisely carried out.
When a magneto-optic recording medium is used, it is preferable that, particularly, in a state in which at least one of the master carrier and the slave medium is heated, the master carrier and the slave medium be closely adhered to each other and a transfer magnetic field be applied thereto. The heating temperature is preferably in the range from 100 to 300xc2x0 C., and more preferably in the range from 150 to 250xc2x0 C. In the above-described temperature range, coercive force Hc decreases and recording (writing) can be easily carried out.
In the above-described manufacturing method of an information recording medium, the predetermined direction can be made perpendicular to the surface of the disk. Due to the direction in which the magnetized regions are magnetized being made perpendicular to the surface of the disk, there is no possibility that the magnetized regions magnetized in different directions and alternately arranged in the radial direction of the disk may weaken magnetic force one another. As a result, the magnetic force of each magnetized region becomes stable.